Seismic response study of ordinary and isolated bridges crossing strike-slip fault rupture zones

摘要

This article presents a comprehensive parametric study of ordinary and seismically isolated bridges crossing strike-slip faults by performing nonlinear response history analysis using actual near-fault ground-motion records and by varying the fault crossing angle, fault crossing location, pier height, span length, seismic excitation polarity, and number of ground-motion components. The considered ground motions include three records from major earthquakes with their peak ground displacements and pulse periods being considerably larger in the fault-parallel component than in the fault-normal component and one record from a strong earthquake with comparable peak ground displacements and pulse periods in both components. The analysis results indicate that fault crossing angle and fault crossing location significantly affect the displacement demands, the distributions of peak displacement responses at piers and abutments, and the deformed shapes of both ordinary and seismically isolated bridges. The most advantageous scenario is generally obtained at a fault crossing angle of 90 degrees and a fault crossing location at the middle span of the bridge. In addition, the variation trends of isolation displacement demands and pier drift demands of seismically isolated bridges with fault crossing angle and fault crossing location appear to depend primarily on earthquake magnitude. Based on the limited number of considered records, it is also observed that utilizing only the fault-parallel ground-motion component is generally sufficient for the seismic analysis of bridges crossing strike-slip faults, with the exception of seismically isolated bridges subjected to records from smaller earthquakes. Furthermore, the effect of seismic excitation polarity on the displacement demands of ordinary and seismically isolated bridges may be significant depending on the fault crossing angle. Finally, pier height and span length are found to have an insignificant effect on the displacement demands of bridges crossing strike-slip faults.